Magnetic circuit comprising one or more stacked plates



April 4, 1950 J. BROUWER 2,503,092

P. H. MAGNETIC CIRCUIT COMPRISING ONE OR MORE STACKED PLATES Filed May 13, 1948 JIHERWRIKJO/[ANAESBROUVER INVENTOR.

ATTORHY Patented Apr. 4, 1950 MAGNETIC CIRCUIT COMPRISING ONE on MORE STACKED PLATES Pieter 'Hendrik Johannes Netherlands, assignor t Brouwer, Eindhoven, 01; Hartford National Bank and Trust Company, Hartford, Conn., as

trustee Application May 13, 1948-, Serial No. 26,866 Inthe Netherlands June 5, 1947 .This; invention relates toa magnetic circuit; for example fordynamos'or. motors; which comprises one or more stacked plates-wherein each of the plates-{is provided with; a numberuof poles arranged onedgeand bentover. with respect to the plate," the poles consisting oftags of each of the plates-which are-foldedglengthwise soas to be U-shaped, in such manner that the ends of the limbs ofthe U are located on a surface of revo- Tuti n p I, I I. M

The poles arranged on (edge haveytheuknown advantage that.; the-,transition= of;.the magnetic lines of forceiat-the; airgapwwhichis located at thesaid surface of revolutione-from or towards the poles is not afiected'bythe'reluctance prevail-, ing between-the laminations.--

The .taggfolded on; theirjaxis of length constitute, in mechanical respect, very rigid poles which are not required to be'reinfo'rced' or otherwise secured. The term axis of length of the tags is to be understood to mean the axis located-between the two edges of a ta ,..these edges constituting, after having been folded, the sides onedge of the poles.

The invention .is particularly; suitable for. use with hub dynamos for bicycles, in which a very great number of poles is desirable.

In order that the invention may be more clearly understood and readily carried into effect, it will now be described more fully with reference to the accompanying drawing which represents embodiments thereof, given by way of example.

Figures 1 and 2 represent diagrammatically a plan view and a side view of part of the magnetic circuit according to the invention.

Figs. 3 and 4 show a magnetic circuit comprising three plates.

In Fig. 1 a plate is provided with a plurality of punched tags 2 which extend in a more or less tangential direction. The tags 2 are folded on their axis of length 3, so as to be U-shaped, in a direction away from the observer. The commencement of this folding operation is illustrated with reference to tag 4. The folding operation is preferably carried out to such an extent that the two inner surfaces 5 of the tag substantially coincide. Prior to, during or after the folding operation the tag is bent towards the observer, preferably at right angles to the plane of the drawing. In this manner poles 6 arranged on edge, are obtained, the ends 'I of the limbs of the U 8 thus being approximately located on a cylinder surface 9. An annular, permanent magnet comprising a number of magnet poles may be arranged to surround this cylinder surface, for ex- Til iii)

ample to produce'an E. M. F. in an annular coil (not, represented for the sake of simplicity) which is arranged between the poles G and a cylindrical recess In in the central part of the plate I. Fig. 2 is a side view of a pole E of the plate I and the central cylinder Ill. In order to complete the coil circuit an exactly identicalbody comprising poles is. introduced with the central cylinder into the annular coilin suchmanner that the poles of this second body are in. interfitted relationship with the poles 6 of the plate I, the central cylinder resting on the cylinder III.

In Fig. 1 the ends of the limbs of the U of the pole- I I are bevelled by grinding as indicated at I2, so as to be parallelto the cylinder surface 9, .in order to enlarge the pole surface adjacent the air gap- In addition this surface coincides better with the cylinder surface 9, so that the air-gap has the samewidth throughout.

Part of Fig. 1 shows another embodiment in whichiuse is made of radial tags I3 which are folded. together and bent to form poles I 4 in the manner described above. This embodiment permits the use of a larger number of tags than in the case of tangentialtags, so that the number of poles may also be increased.

If the bending over of the poles with respect to the plate I is elfected through an angle (Fig. 2) of less than 90, it is possible to obtain a pole I5, of which Fig. 1 is a plan View and Fig. 2 a side view. In every perpendicular section of this pole the limbs of the U become shorter and shorter according as the section approaches the free end of the pole. This means that the thickness of the pole decreases towards its end as appears from the side view of the pole I5 in Fig. 2. Such a pole may be formed either by folding the wedgeshaped tags or by grinding or turning off the su perfiuous material outlined by the dotted line in Fig. 2.

Figures 3 and 4 finally show one quarter part of a magnetic circuit for a bicycle hub dynamo, comprising three members shown in Figs. 1 and 2 which are arranged one within the other. The space between two successive poles ll of one and the same member I8 is chosen to be so large that two poles I 9 and 20 of the second and third member 2| and 22 respectively are adapted to be provided in between. The three central, cylindrical parts 23 to 25 also fit into one another.

The circuit thus built up has a pole width 25 which is double the thickness of the plate, the thickness of the remaining part of the magnetic circuit being three times the thickness of the plate.

The three plates are secured together, for instance with the aid of rivets 21 represented diagrammatically.

In the manner set out with reference to Figures 1 and 2 this coil-circuit also is completed by arranging a second body in reverse position.

It has finally proved very important to saw through the magnetic circuit at one point as shown at 28 in Fig. 3 by way of example, thus raising the power from 1.1 to 1.8 watts in a test circuit.

What I claim is:

1. A magnetic circuit arrangement for bicycle dynamos and the like, comprising a plurality of plates of magnetic material in stacked relationship, each of said plates having a plurality of pole-shoes, each of said pole-shoes comprising a tag-like projection of said plate bent over with respect thereto and in edge-wise relationship therewith and having a generally U-shape, the pole-shoes being arranged in such manner that the ends of the limbs of the U are located on a surface of revolution to provide a plurality of poles arranged on edge about the periphery of the plate.

2. A magnetic circuit arrangement for bicycle dynamos and the like, comprising a plurality of generally circular plates of magnetic material in stacked relationship, each of said plates having a plurality of pole-shoes extending tangentially from the periphery of the plate, each of said pole-shoes comprising a tag-like projection of said plate bent over with respect thereto and in edge-wise relationship therewith and having a generally U-shape, the pole-shoes being ardynamos and the like, comprising a plurality of I generally circular plates of magnetic material in stacked relationship, each of said plates having a plurality of pole-shoes extending radially from the periphery of the plate, each of said pole- 4 shoes comprising a tag-like projection of said plate bent over with respect thereto and in edgewise relationship therewith and having a generally U-shape, the pole-shoes being arranged in such manner that the ends of the limbs of the U are located on a surface of revolution to provide a plurality of poles arranged on edge about the periphery of the plate.

4. A magnetic circuit arrangement for bicycle dynamos and the like, comprising a plurality of plates of magnetic material in stacked relationship, each of said plates having a plurality of pole-shoes, each of said pole-shoes comprising a tag-like projection of said plate bent over with respect thereto and in edge-Wise relationship therewith and having a generally U shape, each of said U-shaped tag-like projections having limbs which decrease in length toward the outer end of the tag-like projection, the poleshoes being arranged in such manner that the limbs of the U are located on a surface of revolution to provide a plurality of poles arranged on edge about the periphery of the plate.

5. A magnetic circuit arrangement for bicycle dynamos and the like, comprising a plurality of annular plates having a narrow radial slit therein of magnetic material in stacked relationship, each of said plates having a plurality of poleshoes, each of said pole-shoes comprising a taglike projection of said plate bent over with respect thereto and in edgewise relationship therewith and having a generally U shape, the poleshoes being arranged in such manner that the limbs of the U are located on a surface of revolution to provide a plurality of poles arranged on The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Rathmann Dec. 14, 1937 Number 

